Integrated circuit comprising a DAC with provision for setting the DAC to a clear condition, and a method for setting a DAC to a clear condition

摘要

A multi-channel integrated circuit comprises a plurality of channels (CH 1 to CH 20 ). A DAC ( 3 ) is provided in each channel (CH 1 to CH 20 ) for converting digital data inputted to the circuit ( 1 ) through an I/O port ( 14 ). Digital data to be converted by the DACs ( 3 ) is selectively applied to input registers ( 10 ) of each channel (CH 1 to CH 20 ) on a digital data bus ( 16 ) under the control of an interface and control logic circuit ( 15 ). The digital words written to the input registers ( 10 ) are in turn written to DAC registers ( 9 ) through corresponding digital switches ( 12 ) for conversion by the DACs ( 3 ). A clear code register ( 22 ) stores a clear code for writing to the DAC registers ( 9 ) in response to a clear signal applied to a clear terminal ( 24 ) of the circuit ( 1 ) so that analogue outputs appearing on output terminals ( 5 ) of the channels (CH 1 to CH 20 ) are of a predetermined value, typically, zero volts, when the circuit ( 1 ) is set in a clear condition. The clear code is written to the clear code register ( 22 ) through the I/O port ( 14 ) and the interface and control logic circuit ( 15 ).